This application claims priority from Korean Application No. 2001-61512, filed Oct. 5, 2001, the contents of which are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to an apparatus for heating a substrate during a semiconductor device fabricating process. The invention also relates to a substrate processing apparatus having a heating apparatus. More particularly, the invention relates to a hot plate having a uniform temperature distribution and a semiconductor wafer processing apparatus that includes the hot plate.
2. Description of the Related Art
Recently, as computers have become more popular, semiconductor devices have become more developed as an information media. As part of this trend, semiconductor devices are required to have higher-speed operation and larger storage capacities. For this reason, semiconductor device manufacturing techniques must be developed to improve the integration density, reliability, and response speed of the semiconductor device.
Conventionally, semiconductor devices are manufactured by successively performing a plurality of unit processes such as a deposition process, a photolithography process, an etching process, an ion implanting process, a polishing process, a cleaning process, etc. A process for forming a layer on a substrate, a process for baking a photoresist composition on the substrate, and a process for removing a photoresist pattern used as a mask on the substrate are each performed by heating the substrate to a high temperature.
Precise control of the temperature of an apparatus for heating the substrate is required in current semiconductor fabrication processes that require a design rule of less than 0.15 mm. If the temperature of the substrate is not uniform, a pattern cannot be uniformly formed on the substrate. A non-uniform pattern lowers the reliability of the semiconductor device.
FIG. 1 is a schematic cross-sectional view of a conventional apparatus for heating a substrate. Referring to FIG. 1, a process for manufacturing the substrate is carried out in a chamber 100. A heater 102, for heating the substrate, is connected to a lower portion of the chamber 100. The heater 102 includes a lamp 104 and a quartz plate 106 installed over the lamp 104. A light radiated from the lamp 104 heats a hot plate 108, on which the substrate is placed, through the quartz plate 106. The hot plate 108 is made of aluminum because it has a relatively high thermal conductivity.
A temperature sensor 110 is installed on a peripheral portion of the hot plate 108. A controller 112 is connected to the temperature sensor 110. The controller 112 generates a control signal to control a temperature of the hot plate 108 based on a signal from the temperature sensor 110. A power supply 114 provides the lamp 104 with electric power by receiving the control signal.
Unfortunately, a temperature differential arises in the material of the conventional hot plate 108 during the process for manufacturing the substrate. The temperature differential results in process defects. A heater that uses a hot wire installed on a lower surface of a hot plate to heat a substrate encounters similar problems due to a temperature differential across the hot plate. If the hot plate 108 temperature is non-uniform, the thickness of a layer formed on the substrate during a deposition process will not be uniform. The thickness of a pattern formed on the substrate in an etching process is also not uniform if the hot plate 108 temperature is non-uniform. Additionally, the temperature differential results in the thickness of a photoresist layer in a baking process being non-uniform. Further, the photoresist layer will not be completely removed in an ashing process when the temperature is non-uniform.
The problems caused by the temperature differential become more severe as the diameter of the substrate becomes larger. Accordingly, the industry has made several attempts to modify the heater structure as well as the material used in order to solve the temperature differential problem. For example, U.S. Pat. No. 5,294,778 issued to Carman, et al. discloses a heating system that includes a spiral shaped main resistance heater and two single turn edge loss graphite resistance heaters. One of the edge loss graphite resistance heaters is located within the inner diameter of the main spiral shaped resistance heater and the other is located along a periphery of the outer diameter of the main resistance heater.
U.S. Pat. No. 6,207,932 issued to Yoo discloses a body member having a wafer support. A gas line provides a processing gas to the wafer support. A heater block provides the heated elements with electric power and temperature control. In Yoo, however, the heater maintains a constant hot plate temperature to reduce the processing time of the unit processes. Accordingly, the thermal efficiency of the heater is decreased and energy loss of the heater is increased.
Various principles of the present invention provide a solution to the foregoing problem. According to these principles, a substrate heating apparatus includes a hot plate that maintains its heat as well as a uniform temperature distribution.
More particularly, according to one aspect of the present invention, an apparatus for heating the substrate comprises a heater for heating the substrate and a hot plate, on which the substrate is placed. The hot plate is preferably a composite plate including a plurality of plates each having a different thermal conductivity from each other. The substrate is then heated by heat provided from the heater.
In one embodiment of the present invention, the hot plate includes a first plate having a first thermal conductivity. A second plate having a second thermal conductivity is laminated on an upper surface of the first plate. The first plate can, for example, be made of aluminum and the second plate can be made of stainless steel or titanium.
In another embodiment, the hot plate includes a first plate formed of a material such as aluminum having a first thermal conductivity. A second plate is laminated to an upper surface of the first plate and a third plate is laminated to a lower surface of the first plate. In this embodiment, the second plate and the third plate are preferably formed of a material such as stainless steel or titanium having a second thermal conductivity.
In a still further embodiment, the hot plate includes a first plate made of a material such as copper having a first thermal conductivity. A second plate is laminated to an upper surface of the first plate. A third plate is laminated to an upper surface of the second plate. In this embodiment, the second plate is preferably made of a material such as aluminum having a second thermal conductivity. The third plate is preferably made of a material such as stainless steel or titanium having a third thermal conductivity.
According to yet another aspect of the present invention, the heater can include a hot wire therein or a lamp radiating a light. The hot wire and lamp generate heat by receiving electric power. The apparatus for heating the substrate may further include a sensor installed at an edge portion of an upper surface of the hot plate for sensing a temperature of the hot plate. A controller can be connected to the sensor to control the temperature of the hot plate using a signal from the sensor.
A composite plate constructed having a plurality of plates with different thermal conductivities provides a uniform temperature distribution when heating a substrate. Accordingly, using the above-described embodiments, the substrate placed on the hot plate can be uniformly heated. Furthermore, the energy required to keep the hot plate at a constant temperature is reduced. Accordingly, the composite plate is able to heat the substrate at a constant temperature.
According another aspect of the present invention, an apparatus for manufacturing a substrate comprises a chamber for performing the substrate manufacturing process. A gas supply provides an inside of the chamber with gas for the process. Means for heating the substrate comprises a heater arranged in the chamber to provide heat for heating the substrate. A hot plate, on which the substrate is placed, includes a composite plate formed from a plurality of plates having different thermal conductivities from each other. The substrate is heated by heat supplied from the heater. A process for removing a photoresist layer formed on the substrate and a process for forming a layer on the substrate using plasma can also be performed in the chamber.
According to a still further aspect of the present invention, an apparatus for manufacturing a substrate comprises a chamber. A process for baking a photoresist layer on the substrate is performed in the chamber. Means for heating the substrate includes a heater arranged in the chamber to provide heat in order to heat the substrate. A hot plate, on which the substrate is placed, is preferably made of a composite plate having a plurality of plates each having a different thermal conductivity. The substrate is heated using heat from the heater.
According to the foregoing principles of the present invention, because the hot plate provides a uniform temperature distribution, process failures resulting from the non-uniform temperature distribution of the hot plate can be reduced. In other words, layers formed on the substrate have a uniform thickness and a photoresist layer on the substrate can be more effectively removed. In addition, the photoresist layer baked by the hot plate will have a more uniform thickness. The reliability and productivity of a semiconductor device manufacturing apparatus, as well as the devices manufactured therein, are also improved.